Spark plug



. Feb. 6, 1940. NCWOSIELSK] 2,189,435

SPARK PLUG Filed Oct. 7, 1938 IN V EN TOR.

ATTORNEY Patented Feb. 6, 1940 UNITED STATES PATENT cries SPARK Application October 7, 1938, Serial No. 233,712

Claims.

provide a radio-shielded spark plug wherein novel means are employed for securing electrical insulation in position therein.

Still another object is to provide a spark plug having the center electrode thereof insulated in a novel manner to minimize the danger of flashovers and hence increase the operating efficiency thereof.

A further object is to provide a novelly constructed spark plug which may be more inexpensively manufactured than similar devices heretofore known.

A still further object is to provide a novel spark plug wherein heat is conducted from the vital parts thereof with greater facility than in prior devices of the same character.

5 Another object is to provide novel means in a spark plug for electrically connecting the center electrode thereof to a current carrying conductor.

The above and further objects and novel features of the invention will more fully appear go from the following detailed description when the same is read in connection with the accompanying drawing. It isto be expressly understood, however, that the drawing is for the purpose of illustration only and is not intended to define 35 the limits of the invention, reference for this latter purpose being had primarily to the appended claims.

In the drawing wherein like reference characters refer to like parts throughout the several 40 views,

Fig. 1 is a side elevation, partly in section and with parts broken away, of one form of spark plug embodying the present invention; and,

Fig. 2 is a bottom view of said spark plug.

45 A single embodiment of the invention is shown in the drawing, by way of example only, in the form of a radio-shielded spark plug of the type employing mica insulation and adapted for use .on high powered aircraft engines and the like.

50 As illustrated, said spark plug comprises a novel body or shell 5 which has a grounded electrode 6 formed integrally therewith. In the process of manufacturing body 5 the same is formed with a closed bottom and diametrically opposed portions thereof are thereafter cut away along surfaces 1 and 8 (Fig. 2), thus leaving the barlike electrode 6 extending across the open end of the body. Since the electrode and body are integral, instead of being soldered or brazed together in the usual manner, it will be seen that 5 heat is more readily conducted from the former to the latter and thence to the surrounding atmosphere or other cooling medium. The lower end of body 5 is provided with external threads 9 for engagement with a threaded opening in an 10 engine cylinder (not shown), whereby electrode 6 is grounded through the engine frame.

Supported within shell 5 on an internal shoulder I0 is a novelly constructed center electrode w assembly which constitutes a readily removable unit that is efliciently insulated against flashovers. undesirable between the center electrode and grounded portions of the plug. In the form shown, said unit comprises a central metallic spindle or electrode having an elongated stem l l and an enlarged head l2, all but the upper end of said stem having a drive fit in an expansible tube l3 of soft metal, such as copper. Said tube and center electrode are supported in shell 5, with head l2 of said electrode adjacent grounded electrode 6, by means of a tubular supporting member I 4 which is preferably made of metal having high heat conductivity.

Tube 13 and stem II extend through a .central bore in member l4 and are insulated therefrom, in part, by a sleeve or cigarette l5 of mica, or other suitable insulating material, which extends the entire length of tube 23. Closely surrounding the lower end of sleeve l5 and interposed as spacing means between member l4 and electrode head I2 is a stack of insulating washers l6 made of mica or other suitable insulating material. The upper end of stack l6 may extend into the enlarged bore of a downwardly extending portion I! of member H. To further insulate tube I3 from member (4, a second mica sleeve or ciga rette l8 extending from the top of stack I6 to the upper end of tube i3 surrounds mica sleeve l5 and closely engages the inner surface of the bore through member l4. Additional insulation is provided about the upper end of center electrode H in the form of a stack of washers I9 made of mica or other suitable insulating material. The latter stack rests upon the upper surface of member l4 and is capped by a metallic washer 20 which preferably closely engages the upper marginal portion of insulating sleeve l5, {8. A

second metallic washer 2| is seated in an en-- larged bore in washer 20 and closely surrounds the projecting upper end of stem or spindle H.

The latter. is counterbored and peened over 7 against washer 2| to secure mica stack [9 in position and hence make the central electrode assembly a rigid unit.

The novel center electrode unit above described is centrally supported in shell 5 by means of a peripheral flange 22 on member 14 adjacent the lower end of the latter, which flange rests upon internal shoulder Ill. The unit is secured in shell 5 by a gland nut 23 which is threadedly received by the upper end of said shell and operatively engages the upper surface of flange 22. In order to obviate any leakage of gases from the engine cylinder, suitable gaskets 24 and 25,are provided between flange 22 and the adjacent surfaces of parts 5 and 23. Washer or gasket 24 is preferably made of copper or like material and washer 25 may be of steel.

Extending upwardly from and preferably integral with gland nut 23 is a metallic tube or barrel 26, the latter being provided for radioshielding purposes ,as is well understood in the art. Barrel 26 is preferably lined with a novel insulating sleeve 21 of mica or other suitable insulating material which is secured in place in a novel manner. As shown, the inner or lower end of sleeve 2! is positively held in expanded condition by a ferrule or ring 28 to facilitate insertion thereof into barrel 26. Ring 28 engages the inner marginal surface of the sleeve 21 and has an external peripheral flange 29 that extends across the end thickness of sleeve 21 to protect the same against damage during handling thereof and assembly of the plug.

The upper end of sleeve 21 is protected against 6 damage and said sleeve is held in place in barre] 26 by novel means constituted by a sheet metal ferrule 30. The latter is of inverted U- I shape or channel-shape in radial cross-section and encompasses the outer ends of sleeve 2'! and barrel 26. The inner flange of ferrule 30 closely engages and extends parallel with the inner wall of sleeve 21 while the edge of the outer flange of said ferrule is rolled or pressed inwardly, as at 31, beneath 'a small peripheral bead or rib 32 formed on the reduced upper end of barrel 26.

If desired, the outer flange of ferrule 30 may be slo'tted in an axial direction to facilitate the removal thereof from barrel 26.

External threads 33 are provided adjacent the upper end of barrel 26 forthreadedly receiving a nut by means of which a radio-shielding tube for an electrical conductor may be connected with said barrel-in a manner well-known in the art. The insulated conductor (not shown) which is led into barrel 26-through said shielding tube, may be quickly and easily connected to center electrode II by novel inexpensive means constituted by a pointed spike or pin 34 having a drive fit in the counter-bored upper end of said electrode and constituting an extension thereof.

There is thus provided a novel spark plug which is both efficient in operation and rugged in construction and which may be comparatively inexpensively ma ufactured. The novel spark plug provided is a so so constructed as to obviate the prime dangers of overheating and undesirable flash-overs. Additionally, the novel construction of the plug facilitates cleaning and repair thereof and permits replacement of the vital elements without necessitating a complete new plug. The spark plug provided-also embodies novel means for securing an insulated sleeve in the radio shielding barrel thereof.

Although only a single embodiment of the invention has been illustrated and described in detail, it is to be expressly understood that the same is not limited thereto. Various changes may be made in the design and arrangement of parts illustrated, as well as in the particular materials herein specified by way of example, without departing from the spirit and scope of the invention as will now be understood by those skilled in the art. For a. definition of the limits of the invention, reference is had primarily to I the end thickness of the sleeve, and means for securing said sleeve in said tubular portion including a ring-like metallic ferrule having a U- shaped radial section, said ferrule extending over the other end of said sleeve and the outer end of said tubular portion and having the edge' of the outer flange thereof pressed inwardly beneath the external rib on said tubular portion.

2. In a spark plug having an electrode, a metallic barrel surrounding at least a portion of said electrode, an/insulating sleeve lining the inner wall of said barrel, a rigid ring in one end of said sleeve for holding said end in expanded condition, and means for securing said sleeve insaid barrel including a ring-like metallic ferrule, said ferrule extending over the other end of said sleeve and the outer end of said barrel.

3. In a spark plug having an electrode, a metallic barrel surrounding at least a portion of said electrode, an insulating sleeve lining the inner wall of said barrel, and a ring-like ferrule having a channel-shaped radial section, said ferrule extending over the outer ends of said sleeve and barrel.

4. In a spark plug having an electrode, a metallic barrel surrounding at least aportion of said electrode, said barrel having an external rib near the end thereof, an insulating sleeve lining the inner wall of said barrel, and a ring-like ferrule having a channel-shaped radial section, said ferrule extending over the outer ends of said sleeve and barrel and having a portion thereof ,pressed inwardly beneath the external rib on said barrel. 5. In a spark plug having an electrode, a tubular metallic portion surrounding a part of said electrode and having an external rib near the end thereof, an insulating sleeve lining the inner wall of said tubular portion, and means for securing said sleeve in said tubular portion including a ring-like channel-shaped ferrule, the inner flangepf said ferrule having engagement with and extending parallel to the inner marginal portion of said sleeve and the outer flange of said ferrule having the edge thereof pressed inwardly into locking engagement with the external rib on said barrel.

EDWARD B. NOWOSIELSKI. 

